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<h1><a href="../Table_of_Contents.html"><img src="../mpl_logo.jpg" alt="[Home]" border=0 align="right"></a>begin</h1><h3>Synopsis</h3>
<p>
<pre>
template<
typename Sequence
>
struct begin
{
typedef <em>unspecified</em> type;
};
</pre>
<p>
<h3>Description</h3>
<p>
Returns an iterator that points to the first element of the sequence.
<p>
<h3>Definition</h3>
<p>
<pre>
#include "<a href="../../../../../boost/mpl/begin_end.hpp">boost/mpl/begin_end.hpp</a>"
</pre>
<p>
<h3>Parameters</h3>
<table border="1">
<tr><th> Parameter </th><th> Requirement </th><th> Description </th></tr>
<tr><td><code>Sequence</code></td><td>A model of <a href="../Sequence.html">Sequence</a></td><td></td></tr>
</table>
<p>
<h3>Expression semantics</h3>
<p>
<table border="1">
<tr><th> Expression </th><th> Expression type </th><th> Precondition </th><th> Semantics </th><th> Postcondition </th></tr>
<tr><td><code>typedef begin<Sequence>::type first;</code></td><td>A model of <a href="../Input_Iterator.html">Input Iterator</a></td><td></td><td><code>first</code> is an iterator pointing to the first element of the <code>Sequence</code>; equivalent to <code>Sequence::begin</code> unless the algorithm has been specialized for the particular type of sequence.</td><td><code>first</code> is either dereferenceable or past-the-end; it is past-the-end if and only if <code>size<Sequence>::type::value == 0</code>. </td></tr>
</table>
<p>
<h3>Complexity</h3>
<p>
Amortized constant time.
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<h3>Example</h3>
<p>
<pre>
typedef vector<unsigned char,unsigned short,unsigned int, unsigned long> unsigned_types;
typedef begin<unsigned_types>::type iter;
BOOST_STATIC_ASSERT((boost::is_same<iter::type,unsigned char>::value));
</pre>
<p>
<h3>See also</h3>
<p>
<a href="../Iterators.html">Iterators</a>, <a href="../Sequence.html">Sequence</a>, <code><a href="../Reference/end.html">end</a></code>, <code><a href="../Reference/size.html">size</a></code>, <code><a href="../Reference/empty.html">empty</a></code>
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<a href="../Table_of_Contents.html">Table of Contents</a><br>Last edited July 22, 2002 2:03 am</body></html>
